1. Field of the Invention
The present invention relates to a charged particle beam drawing apparatus, and a method of manufacturing an article.
2. Description of the Related Art
In recent years, an electron beam drawing apparatus is expected to be used in the lithography step of a semiconductor process with the tendency to pattern miniaturization due to its high resolution. Japanese Patent Laid-Open No. 09-245708 discloses a multiple electron beam drawing apparatus which splits an electron beam emitted by an electron source into a plurality of electron beams to draw using the plurality of electron beams in parallel.
However, a multiple electron beam drawing apparatus especially uses a column and a substrate with a narrow gap between them, although this arrangement is not limited to a multiple electron beam drawing apparatus. This makes it difficult to implement a measuring device which directly measures the position (surface shape), in the Z-direction, of the substrate arranged below the column. To combat this problem, the position of the substrate in the Z-direction can be measured while it is arranged at a position different from that below the column, and the position of a substrate stage relative to a Z reference mirror in the Z-direction can be controlled based on the measured value, thereby controlling the position of the substrate in the Z-direction. Unfortunately, in this method, the flatness of the Z reference mirror becomes an error factor of Z-direction position measurement, thus degrading the drawing precision.